Welhead templates

ABSTRACT

A drilling and production template for sub-sea wells comprises a plurality of individual limbs ( 1-4 ) each with a central hub ( 10-14 ) at one end of an arm ( 11-41 ) and a drilling receptable ( 12-42 ) on the other end of the arm. The hubs are of different diameters such that they fit within each other in a telescopic manner. They have cut-out ( 27, 37, 47 ) accommodate the arms of the other limbs when installed. The template may be deployed onto a pre-installed foundation with the arms stacked vertically above the other, in such manner as to pass through the moonpool of a drilling vessel. The complete assemblies are installed on a mechanical running tool attached to a drilling string. After the template is disposed on the foundation, the drilling string is rotated, causing the running tool to rotate the limbs ( 1-4 ) so that the hubs telescope into each other, providing a splayed multi-well drilling and production template.

FIELD OF THE INVENTION

This invention relates to templates for use sub-sea, that is to say ator adjacent the bottom of the sea or other body of water and intended toprovide guides for the drilling of sub-sea wells for petroleum or otherliquid or gaseous hydrocarbons and also to provide, preferably, asub-sea frame for a manifold and other means by which hydrocarbons areextracted from the wells and hydraulic and other control lines areconnected to the wellhead.

BACKGROUND TO THE INVENTION

It is customary to provide a wellhead template in the form of a rigidframe which includes several spaced-apart guides for drilling pipes.Such a template is deposited on or adjacent the sea bed in a desiredlocation, with or without the aid of ancillary supports, and acts as atleast an initial guide for drilling strings for up to the number ofwells that can be be positionally defined by the template. It iscustomary for the multi-well template to support, during the extractionor production phase manifolds, ‘Christmas trees’ and other knownequipment employed for the extraction of the liquid or gaseoushydrocarbons and the control of the process of extraction.

Known rigid templates as described in the foregoing exhibit severalpractical disadvantages. For example it is preferable to lower thetemplate to the sea bed through an aperture in a drilling vessel knownas a moonpool. Although moonpools are substantial in size, beingtypically rectangular of the order of 5 or 6 meters in breadth and 6 or7 meters in length, they are, necessarily, limited in extent. On theother hand, it is often desirable to provide an inter-well spacing whichshould require, typically, a four-well template to be of the order of 20meters by 20 meters. Although these figures are given only as typicalexamples, there is in any event a practical limitation on the size of arigid template which can be deployed through a moonpool.

It is known to provide a multi-well template comprising relativelyhinged parts so that the template can be deployed through the moonpoolin a folded configuration and be subsequently unfolded to lie flat on oradjacent the sea bed. However, not a great increase in lateral extentcan be achieved using a hinged template and deployment of it isinconvenient.

A further disadvantage of both rigid and hinged templates is theiroccupancy of space between the positions of the well. It is oftendesirable to provide additional satellite wells in the vicinity of theoriginal drilling and it may be desirable to dispose those wells withina region generally bounded by the wells of the original template.However, with known rigid or hinged templates all subsidiary orsubsequent wells must be disposed outside the general area of thetemplate and there is therefore not only a constraint on the positioningof satellite wells but added complexity or difficulty in establishingfluid connections between the template manifold and the satellite wells.

It is known from GB-A-2003532 to provided a well template which has two‘scissor’ arms each having a well guide at each end. The template isintended to float in a splayed condition.

The object of the invention is to provide an improved multi-welltemplate. Although, as will be apparent the invention is more broadlydefined hereinafter, a preferred drilling and production template forsub-sea wells in accordance with the invention comprises a plurality ofindividual limbs each comprising a hub connected by an arm to a drillingguide. The hub may be at one end of the arm and the drilling guide maybe at the other end of the arm. The hubs or central supports arepreferably of differing diameters so that they fit one within another ina ‘telescopic’ manner. The hubs have mutually engaging parts, preferablyin the form of cut-outs or axial slots, which can accommodate the armsof other sections when they are installed. Such a template may bedeployed onto a foundation from a drilling vessel with the limbs in aclosed configuration and in particular with the arms stacked verticallyabove each other. In such a configuration the assembly may pass throughthe moonpool of the drilling vessel or platform. The assembly of limbsmay be installed on a mechanical running tool attached to a drillingstring. After the assembly lands on an appropriate foundation, thedrilling string may be rotated to cause the running tool to rotate thelimbs so that they fan out into a desired open configuration. Thetemplate preferable as indicated includes indexing slots which operateas the arms fan out so as to fix the arms in predetermined angularpositions relative to each other. In particular, the slots ma bearranged so that as each arm is rotated relative to its neighbour it canenter the slot in the neighbour and close axially relative to theneighbour. Preferably the cut-outs or slots are arranged so that thehubs telescope into each other to provide the template with aconfiguration in which the arms radiate in approximately the same commonplane. After the wells are drilled a suitable manifold may be installedon the centre of the structure.

Particular examples of the invention will be described in the following,with reference to the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates one embodiment of the invention, in an initialconfiguration and deployed on a pre-installed sub-sea foundation;

FIG. 2 illustrates the template in relation to a typical moonpool;

FIG. 3 illustrates the template in an open or final configuration;

FIG. 4 illustrates the template and a typical manifold and ancillaryequipment; and

FIG. 5 illustrates the template in an inverted configuration.

DETAILED DESCRIPTION

FIG. 1 illustrates a rotary template according to the invention in a‘stacked’ or initial configuration. For convenience the template isshown as deployed on a pre-installed sea-bed platform 50, as will bedescribed later.

The template comprises a plurality of individual limbs. In thisembodiment there are four limbs, intended to be finally deployed atright angles to each other. A different number of limbs, in particularfrom three to six inclusive, could be used.

The limbs are generally similar. A first limb 1 comprises a hub 10,which is preferably in the form of a cylindrical tubular support, an arm11 which extends from the hub 10 laterally outwardly, and a drillingreceptacle or guide 12. As illustrated, the hub 10 and the receptacle 12are at opposite ends of the arm 11 but different arrangements arepossible. It is normally desirable to maximize the distance between thehub 10 and the receptacle 12 for a given length of arm 11.

The receptacle 12 may be part of a guide base 13 containing receptacles14 for guide posts and a structural framework 15 including braces 16(not shown in FIG. 1).

The second limb 2 comprises a hub 20, an arm 21 and a drillingreceptacle 92. The arm 21 resembles the arm 11 and the receptacle orguide 22 resembles guide 12. Hub 20 is a cylindrical support tube whichis slightly larger than the tube constituting hub 10 so that hub 10 fitswithin and is rotatable relative to hub 20. Furthermore, hub 20 has acut-out 27 defining an axial slot which is wide enough to accommodatethe arm 11 whereby when arm 11 is rotated relative to arm 21, arm 11will reach a position wherein it can drop into the slot 27 and bethereby indexed in a fixed angular position relative to arm 21. Theupper edges of the slot are outwardly flared at 28 to facilitate theentry of the arm into slot 27.

The third limb 3 has a hub 30, which is again a cylindrical support tubewithin which the hub 20 can rotate, an arm 31 resembling arms 11 and 21and a drilling receptacle 32 resembling receptacles 12 and 22. The hub30 has slots, of which only one slot 37 is shown. Each of these slotsresembles slot 27. These slots in hub 30 can accommodate arms 11 and 21so that these arms will be in a fixed angular position relative to arm31 when arms 11 and 21 have been rotated to enable the arms to drop intothe respective slots in hub 30.

Correspondingly, the fourth limb 4 has a hub 40 with slots, of whichonly slot 47 is shown, for the accommodation of arms 11, 21 and 31whereby, for the particular embodiment, when arm 11 has been rotatedthrough 270 degrees from the initial stacked position all the hubs aretelescoped together and the arms 11, 21, 31 and 41 are fanned out atright angles to each other in a rigid configuration, the arms being insubstantially the same rotary plane. Arm 41 resembles the other arms 11,21 and 31 and receptacle 42 resembles receptacles 12, 22 and 32.However, receptacle 42 may have a splayed foot 48 since it will be thelowermost and the foot may be required to rest on the sea bed.

Also shown in FIG. 1 is a pre-installed foundation 50 comprising a baseplate 51, stabilising feet 52 and a receiving pipe 53 which tapers to asharp edge at its lower extremity 54 and is flared at its upperextremity 55 so that the lowermost hub 40 can easily enter the pipe 53notwithstanding initial misalignment.

A template as described has several practical advantages. It is simpleto fabricate. It can be assembled in a moonpool as explained below and asimple running tool can be used for both installation and deployment.

The deployment of the template will be described with the aid of FIGS. 2and 3.

A normal preliminary to the deployment of the template is the provisionof a foundation, which will be engaged by, and will serve to support,the telescoped hubs of the template. The foundation may be a drilled 30inch (760 millimeter) conductor, a drilled 60 inch (1512 millimeter)pile, a ‘mud-mat’ or any combination which will suit the conditions ofthe soil. The foundation shown in FIG. 1 is an ordinary mud-mat.

The individual limbs 1 to 4 may be lifted onto the production rig eitheras individual units or in pairs, depending on their size and weight. Theindividual arms may be ‘skidded’ into the moonpool and stacked, in aconfiguration as shown in FIG. 1. A running tool, with a suitable drillpipe attachment device is engaged in a lifting connection and theassembly may be run down to the sub-sea location on the drill pipe intothe pre-installed foundation. The running tool will be disengaged fromthe lifting connection and caused to enter the hubs. The running toolwill be used to rotate the hubs so that the topmost limb will rotate (inthis example) 270 degrees. As the arms in each limb reach a positionover the respective slot in the adjacent lower arm, the arms will dropinto their slots so that the hubs telescope together.

FIG. 2 illustrates the limbs of the rotary template in a stackedconfiguration in relation to a moonpool 60. Only the uppermost arm 11 isshown. As may be seen, the moonpool can accommodate a stacked templateof which the effective or overall length of the limbs occupies most of adiagonal dimension of the moonpool 60.

FIG. 3 illustrates the template in its open or fanned-out configuration,with adjacent arms of arms 11, 21, 31 and 41 being set at right anglesto each other. Guide bases 23, 33 and 43 on respective arms 21, 31 and41 correspond to guide base 13 on arm 11. The moonpool is shown by thesuperimposed rectangle 60. In the splayed configuration the distancebetween at least two of the guides (and in this embodiment therespective distance between any two guides) is substantially greaterthan the length of any of the arms.

The running-tool may be disengaged and recovered the wells will bedrilled through the guide plate receptacles either partially orcompletely.

A typical next stage is the assembly of a manifold onto the template.FIG. 4 illustrates the four arms 11, 21, 31 and 41 extending from thehubs 10, 20, 30 and 40 to the receptacles 12, 22,32 and 42 and amanifold assembly comprising a central manifold block 70 located on thehubs. The manifold assembly may be adapted to index to the hub 10.Further assembly may take place in known manner, including thedisposition of ‘Christmas trees’, the making up of flow line connectionsin the normal vertical manner, and the completion of controlconnections.

FIG. 5 illustrates a similar embodiment to that shown in FIG. 1, shownin an inverted manner wherein the hub 40 is uppermost and the lowermosthub 10 has a foot 18 for resting on the sea floor. This embodiment isotherwise very similar to that shown in FIG. 1 and it may be deployed ina similar manner. The hub 40 will be rotated and the slots 27, 37, 47etc will drop onto the arms 11, 21 and 31 in a manner corresponding tothat described with reference to FIG. 1.

What is claimed is:
 1. A sub-sea well template comprising a plurality oflimbs (1-4) each of which comprises an arm (11-41) having a hub (10-40)at one end and a drilling guide (12-42) at the other end, the hubsfitting one within another for rotation about a common axis and thelimbs being mutually rotatable from a configuration wherein the arms areclose together to a configuration in which the arms are widely splayed.2. A template according to claim 1 and further comprising means (27, 37,47) for indexing the arms in the splayed configuration.
 3. A templateaccording to claim 2 wherein the indexing means (27, 37, 47) compriseslots in the hubs disposed such that as the limbs rotate, at least oneof said arms can enter a respective slot in at least one of said hubsand be thereby retained in fixed angular position.
 4. A templateaccording to claim 3 wherein each hub (10-40) comprises a cylindricalpipe.
 5. A template according to claim 4 wherein the slots (27, 37, 47)are open-ended slots in respective hubs.
 6. A sub-sea well templatecomprising a plurality of limbs (1-4) each of which includes an arm(11-41) connecting a respective hub (10-40) and a respective drillingguide (12-42), the hubs fitting together for rotation about a commonaxis, and the limbs being mutually rotatable from a first configurationwherein the arms (11-41) are close together to a second configuration inwhich the arms are widely splayed, the distance between at least two ofthe drilling guides (12-42) in the second, splayed configuration beingsubstantially greater than the overall length of any of the arms.
 7. Atemplate according to claim 6 wherein the arms (11-41) are stacked oneabove another in the first configuration.
 8. A template according toclaim 6 wherein the hubs include indexing slots (27,37,47) each of whichcan receive one of the arms, whereby the arms can be retained in fixedangular positions.
 9. A sub-sea well template comprising a plurality oflimbs (1-4) each of which includes a respective hub (10-40) and adrilling guide (12-42) connected by a respective arm (11-41), whereinthe limbs fit together for rotation about a common axis and the limbsare mutually rotatable from a first configuration in which the arms(11-41 ) are close together to a second configuration in which the armsare widely splayed, the hubs (10-40) including indexing slots (27, 37,47) each of which can accommodate at least one of the arms as the armsare rotated to the slaved condition whereby the arms are held by theslots in relatively fixed angular positions.
 10. A template according toclaim 9 wherein the slots (27, 37, 47) are disposed so that the hubs(10-40) telescope into each other whereby the arms (11-41) radiate inapproximately the same plane.
 11. A template according to claim 9wherein said limbs comprise at least first, second and third limbs andwherein the respective hub of said second limb has an indexing slotwhich accommodates the arm of the first limb and the respective hub ofthe third limb has two indexing slots which accommodate one each of thearms of the first and second limbs.
 12. A template according to claim 11wherein said limbs include a fourth limb of which the respective hub hasthree indexing slots which accommodate a respective one each of the armsof the first, second and third limbs.